This invention relates to an internal combustion engine and more particularly to an improved, compact and easily manufactured, variable valve driving mechanism for such engines.
In order to improve the performance of internal combustion engines throughout their entire load and speed ranges, it has been proposed to employ a variable valve actuating mechanism that will vary the timing of one or more of the camshafts of the engine relative to the engine crankshaft and/or the degree of lift of the valve. By changing the valve timing and/or lift, it is possible to improve the performance for a variety of specific running conditions.
Conventionally, the variable valve timing mechanisms have employed some form of phase shifting mechanism in the drive of the camshafts so as to achieve the variation in the valve timing. These mechanisms are normally hydraulically operated and employ control valves that are mounted on the engine and which supply controlling pressure to the variable valve timing mechanism. Also the amount of valve lift can also be varied hydraulically.
Generally these control valves are comprised of a valve spool and a valve actuator, normally in the form of an electrically operated solenoid. It has been the practice to mount these valves in proximity to the camshafts so as to simplify the plumbing associated therewith and to avoid pressure losses.
One way this may be done is as shown in U.S. Pat. No. 6,289,861, assigned to the assignee hereof. As shown in that patent, the control valves are mounted so that they extend perpendicularly to the mating faces of the cylinder head and cam caps and in close proximity thereto. As shown in that patent, this results in, the positioning of the actuating solenoid in a vertically upstanding position and projecting substantially through the cam cover for the engine. Although this is acceptable in some applications, in many engine applications such projections are undesirable.
It is, therefore, a principal object to this invention to provide an improved actuating control valve mechanism for the variable valve actuating arrangement of an internal combustion engine.
It is another object to this invention to provide an improved and compact arrangement for mounting the control valve of a variable valve actuating mechanism for an internal combustion engine.
Normally the control valve receives oil from the engine lubricating system and delivers it through passages formed in the cylinder head and/or cam bearing cap to communicate with the variable valve actuating mechanism through passages that are formed in the camshaft and generally extend longitudinally there through. This requires the provisions of several passages including a supply passage and a return passage. The supply passage communicates to one of two chambers of the variable valve actuating mechanism and the return passage is connected to the other of these chambers of the valve actuating mechanism. The pressure in these chambers is varied to change the position of the variable valve timing mechanism to achieve the change in valve timing and/or lift.
Obviously, the provision of these multiple passages presents some problems and generally it has been the practice to form the passages primarily through drillings in the various engine components. This can give rise to several difficulties and also is costly.
It is, therefore, a still further object to this invention to provide an arrangement for the control valve communication with the variable valve timing mechanism wherein at least some of the supply passages can be formed in the interface between mating components without requiring drilling.
The features of the invention are adapted to be embodied in an internal combustion engine comprised of a cylinder head member adapted to be affixed in closing relation with at least one cylinder bore to form a variable volume combustion chamber with a piston reciprocating in the cylinder bore. At least one valve is supported for reciprocation in the cylinder head for serving the combustion chamber. A camshaft is journalled in the cylinder head and a cam cap that is affixed to the cylinder head for operating the valve. A hydraulically operated variable valve actuating mechanism operates the valves from an engine driven shaft and varies the timing and/or lift thereof. A control valve selectively controls the operation of the hydraulically operated variable valve actuating mechanism. The control valve has a spool portion and an operating portion for effecting reciprocation of the spool portion.
In accordance with a first feature of the invention, a fitting opening extends through the cam cap and is aligned with a corresponding fitting opening in the cylinder head. The fitting openings have their axes extending perpendicularly to facing and abutting surfaces of the cam cap and the cylinder head. The control valve is disposed in substantial part in the fitting openings with only a small portion of the control valve operating portion extending through an opening in an associated cam cover and outwardly of the area enclosed thereby.
In accordance with another feature of the invention, the control valve supplies fluid to and exhausts fluid from the variable valve timing mechanism through a plurality of passages formed in the internal combustion engine. At least one of these passages is formed by a recess formed in facing and abutting surfaces of the cam cap and the cylinder head.